Motor-control system.



Nd. 678,853. Patented July 23, l90l. A. H.. mmsmoue.

MOTOR CONTROL SYSTEM.

(Applicationvflled Apr. 8; 1901.)

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Patented July 23, 190i.

A. H. ARMSTRONG.

MOTOR CONTROL SYSTEM.

(Applicafion filed Apr. 8 1901,)

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A. H. ARMSTRONG.

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(Application filed Apr. 8. 1901.)

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Patented July 23, IBM.

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Uwrrnn STATns PATNT Canto.

ALBERT II. ARMSTRONG, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, OF NEW YORK.

MOTOR-CONTROL SYSTEM.

SPEGIF IGATIQN forming part of Letters Patent No. 678,853, dated July 23, 1901.

Application filed April 8, 1901.

To all whont it may concern.-

Be it known that I, ALBERT H. ARMSTRONG, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Motor-Control Systems, (Case No. 1,552,) of which the following is a specification.

My invention relates to control systems for alternating current induction motors, and has for its object to equalize the heating of such motors when they are operated in tandem. In the tandem connection the induced member of the motor which is connected to the source of supply operates to supply current to the inducing member of a second motor the induced member of which is shortcircuited on itself when there are but two motors in the motor equipment or connected to the inducing member of a third motor when there are more than two. When the motor equipment consists of two motors connected in tandem and driving a common load, both of the motors will operate at substantially one-half the speed at which they would run if both were directly connected to the source of supply. With the motors operating thus at substantially half their normal speed the frequency of the currents flowing in the interconnected windings of the two motors will be substantially one-half the frequency of the currents supplied to the first motor in the tandem connection and the frequency of the currents flowing in the induced member of the second motor will be substantially zero. The motor which is directly connected to the source of supply must of course'carry the magnetizing-current for both machines. In addition, since the full frequency and voltage of the source of supply are impressed upon the windings of its inducing member the core loss in this member will be a maximum and the core loss in the induced member half what it would be at zero speed. On the other hand, since the frequency of the currents flowing in the inducing-winding 0f the second motor is only one-half that of the source of supply the core loss in the inducing member of the second motor will be only about half as large as the core loss in the inducing member of the first motor, and the Serial No. 54.849. (No model.)

core loss in its induced member will be nearly negligible. Thus the heating of the motor which is No. 1 in the tandem connection will be very large as compared with the heating of the motor which is No. 2.

My'invention is especially useful in connection with electric-railway systems in which it is frequently the practice to go up heavy grades with the motors connected in tandem. In such systems the energy loss in the N o. 1 motor is often exceedingly large, and this motor may even get dangerously hot when operating on a road having heavy grades, while the second motor remains comparatively cool.

In the practical application of my inven tion I so organize the control system for a plurality of induction-motors that in the tandem connection the motors may be operated part of the time with one motor directly connected to the source, so that it will be No. 1 in the tandem connection, and part of the time with another motor connected directly to the source, so that it will be No. 1, the arrangement being such for any one case that the heating of the several motors during the days run will be substantially equal.

My invention will be better understood by reference to the following description, taken in connection with the accompanying drawings, in which Figure 1 is a diagram ofvone-half of the car wiring and one controller for the tandenr multiple control of two induction-motors, the controller being provided with an auxiliary commutating-switch arranged to change the connections of the motors at predetermined intervals in accordance with the principles of my present invention. Figs. 2 and 3 are diagrams illustrating the motor-circuits for the tandem connection in the two operative positions of the auxiliary commutatingswitch of the controller. Figs. 4, 5, and 6 are views showing the mechanical construction of a controller comprising the switches diagrammatically illustrated in Fig.- 1. Fig. 7 is a diagram of a car-wiring and controllers, showing how my inventionmay be applied without providing the controllers with auxiliary commutating-switches. Fig. 8 is a diagram illustrating the motor-circuits for the tandem connection when one of the controllers of Fig. 7 is in operation, and Fig. 9 is a corresponding diagram illustrating the motorcircuits for the tandem connection when the other controller of Fig. 7 is in operation.

My invention may evidently be applied to a motor-control system in which the tandem connection is only one of a series of connections that may be made as well as to a system in which the motors are operated permanently in tandem, and I have chosen to illustrate my invention as applied to the tandemmultiple system constituting the subj cot-matter of my Patent No. 589,404, dated May 21, 1895.

Referring to Fig. 1 of the drawings, M and M represent the windings of two three-phase induction-motors which are connected, by means of the conductors 14 to 17 and 23 to 29, to a source of supply and to a regulating resistance through the contacts of the controller O. This controller comprises two main controlling-switches P and RS, of which the former operates to control the power connections of the motors and the latter to reverse the direction of motion of the motors, and an auxiliary switch OS for changing the motor connections in a manner hereinafter described. All of these switches are shown with their fixed and movable contacts developed on a plain surface, as is customary in diagrammatically illustrating such structures. The arrangement of the contacts of the switch P is the same as I have shown in my Patent No. 539,401, above referred to. This switch operates to first connect the windings of the motors M and M in tandem with the maximum resistance in circuit with the induced member of the second motor, then-to gradually out out the resistance, then to change the connections from tandem to multiple with a, maximum resistance in circuit with the induced members of both motors, and finally to gradually cut out this resistance.

Inasmuch as my present invention pertains only to the tandem connection, I shall in the following description refer only to the first three positions of the power-switch P in which the tandem connections are completed, reference being made to my aforesaid patent for an explanation of the connections made in the succeeding positions of this switch.

The reversing-switch RS operates only to reverse the connection between two of the motor-terminals and two of the terminals of the three-phase source of supply, thereby reversing the direction of rotation of the motors.

\Vhile I have shown in Fig. 1 only one controller 0 connected to the windings of the motors M and M it is to be understood that the complete equipment for a railwaycar will comprehend two controllers 0, one at each end of the car, as is customary in such equipments, the second controller being connected to the wires 14' to 17 and 23 to 29' at the right of Fig. 1 in the same manner as the controller which is shown is connected.

The purposes of my present invention are carried out in the arrangement illustrated in Fig. 1 by a commutating-switch OS in each controller, which operates in one of its positions to connect the terminals of the motor M to those conductors which lead to the source of supply through the contacts of the power and reversing switches, and the terminals of the motor M to those conductors which lead through contacts on the powerswitch to the short-circuiting resistances and in its other position to reverse these connections, so that the terminals of the motor M will be connected to the source of supply and the terminals of the motor M to the shortcircuiting resistances. These connections I have indicated in Figs. 2 and 3, the former of which illustrates the motor connections in the first operative position of the powerswitch P when the fixed contacts of the commutating-switch OS are in engagement with the range of contacts marked g, and the latter of which illustrates the connections for the same position of the power-switch P when the fixed contacts of the comm utating-switch are in engagement with the range of contacts marked it. In order to trace these connections in Fig. 1, let it be supposed that the re versing-switch RS is so thrown that its fixed contacts 18 to 21 are in engagement with the range of movable contacts a and that the commutating-switch is so thrown that its fixed contacts 22 to 29 are in engagement with the range of contacts g. It now the powerswitch P is moved into its first operative position, in which position the fixed contacts 1 to 17, inclusive, lie along the-line 1 1, circuits may be traced as follows from the three conductors T, T, and G, which when the system is in operation are connected to the terminals of athree-phase source of supply, one of these connections being shown as a ground, for the reason that in the operation of electric railways, for which, as above stated, my invention is particularly adapted, it is customary to complete the circuit between one of the terminals of the three-phase source and one of the terminals of the motors on the cars through the rails and the car-wheels, only two trolley-contacts being used. Starting from the conductor T, a circuit leads through the contacts 1 and 3 of the switch P to the conductor 3, thence through contacts 21 and 20 of the reversing switch to the conductor 20 and through the contacts 22 and 23 of the commutating-switch to the conductor 23 and the terminal of the winding a on the inducing member of the motor h From the conductor T another circuit leads through the contacts 2 and 4 of the power-switch to the conductor 4, thence through contacts 19 and 18 on the reversingswitch to the conductor 18, and through contacts 26 and 27 of the commntating-switch to conductor 27, to which the terminal of the winding b of the motor M is connected. The terminal of the winding is connected permanently. to ground and through ground to the third terminal of the three-phase source. Two of the terminals of the winding on the induced member of the motor M, this winding being indicated by the lines d, e, and f, are connected through the conductors 14: and 15', the contacts 14: to 17 of the controller, and the conductors 16 and 17 to two of the terminals of the corresponding winding of motor M the third terminal of each of these windings being connected to a common ground. Two of the terminals of the remaining winding on the motor M are connected through the conductors 25 and 29 and the corresponding contacts of the comm utatingswitch to the conductors 5 and 6, and thence through the contacts 5 and 8 and 6 and 10 of the power-switch to the resistances R and R The third. terminal of this winding is connected through the ground connection and the contacts 7 and 12 of the power-switch to a third resistance R the other terminals of these three resistances being connected together. It will thus be seen that with the commutating-switch in the position specified the two motors Will be connected in tandem with one of the windings of the motor M, connected to the source of supply, and the corresponding winding of the motor ll/l shortcircuited on itself, this connection being diagrammatically illustrated, as already stated,

in Fig. 2. If, however, the commutatingswitch is so thrown that its fixed contacts 22 to 29, inclusive, are in engagement with the movable contacts marked h, the reversingswitch being supposed for convenience in tracing the circuits to remain in the same position with its fixed contacts 18 to 21 in engagement with the contacts marked a, the circuits between the source of supply and the motors may be traced as follows, with the power-switch, as before, in its first operative position: Starting from the conductor T, a circuit leads, as before, through the contacts l and 8 of the power-switch to the conductor 3 and through the contacts 21 and of the reversing-switch to the conductor 20 and the contact 22 of the commutatingswitch. From this point, however, the circuit instead of continuing through the contact 28, as before, is now completed through the contact 25 and conductor 25, thus leading to the terminal of the winding (t of the motor M Similarly the circuit from the conductor T may be traced through the contacts 2 and 4E of the power-switch to the conductor 4, thence through the contacts 19 and 18 of the reversing-switch to the conductor 18 and the contact 26 of the commutating switch, from which point the circuit is completed through the contact 29 and the conductor 29 to the terminal of the winding 1) of the motor M the terminal of the third winding 0 being permanently connected through ground to the remaining terminal of the source of supply.

The connections between the winding (1, e, and f of the motor M and the winding 01 e f of the motor M remain unchanged, and of the terminals of the winding at b c, which before were connected to the source of supply, the first two are now connected through the conductors 23 and 27 and the contacts 23 and 27 of the commutating-switch to the conductors 5 and 6, which are in turn connected through the contacts 5 and 8 and 6 and 10 of the power-switch to the resistances R and R the terminal of the winding 0 being connected through ground to the third resistance R The connections above traced are illustrated in Fig. 3, in which it will be noted that the motor M which in Fig. 2 is the second motor in the tandem connection, has now become the first motor connected to the source of supply.

The commutating-switch OS might be provided with an operating-handle, so that it could be thrown from one to the other of its operative positions whenever the motorr'nan considered it advisable to make such change; but inasmuch as the object of my invention may be more surely achieved by so arranging the system that the connections must necessarily be changed from time to time I have so arranged the commutating-switch that it will be operated indirectly by one of the main controlling-switches.

The mechanism by means of which the commutating-switch is operated should be so chosen that the motor connections will be changed often enough to prevent any one of the motors from heating excessively, the particular arrangement desirable for any one system being determined by the conditions under which the motors are operated.

In electric-railway systems the condition of the grades along the route is the principal determining factor, and depending on the distribution and character of the same the commutating-switch may be arranged to be operated by the power-switch each time that it is moved from its off position or every third or fourth time, as the conditions under which the motors are operated seem to demand, or by the reversing-switch in case an infrequent operation of the commutatingswitch is sufficient to accomplish the desired results. If the commutating-switch is operated by the power-switch, the motor connections will of course be changed every time that the controller is moved from its off to on position, or at least Whenevera predetermined number of such movements have been made. Such an arrangement will be required whenever the grades are excessive and frequent, so that it isinadvisable to operate the motors over the whole route without change of connections. If the commutating-switches are arranged to be operated by the reversing-switches, the motor connections will be changed at the end of every round trip. If the car is operated in one direction over the line from one controller and in the other direction from the controller at the other end of the car, the change in connection is made-at one or the other end of the line, according to the relative positions of the commutating-switches of the two controllers at the start. Thus if the commutating-switches in the two controllers occupy relatively opposite positions when the car is in motion from one end of the route, the transfer of the control to the controller-at the other end of the car will throw the commutating-switch of that controller into a position such that it will connect the motors in the same relation in the tandem connection as they were previously connected by the commutating-switch of the other controller. If, however, the commutating-switches in the two controllers occupy the same relative positions when the car is starting out from one end of the route, the transfer of the control to the controller at the other end of the car will bring the commutating-switch into a position such that it will reverse the position of the motors in the tandem connection. 1f it is desired that the connections shall be changed at each end of the route, the functions of the contacts of the commutatingswitches may be carried out by a proper relative arrangement of the cont-acts of the two power-switches, and in Fig. 4.- of the drawings I have indicated such an arrangement.

7 The operating means for the commutatingswitch which I have chosen for illustration in the present application is so arranged that the saidswitch will be thrown each time that the main controlling-switch, with which it is operatively connected, is operated; but evidently it might be arranged so as to be thrown only after a predetermined number of such movements have been completed.

Referring to Figs. 4 and 5 of the drawings, which illustrate the controller construction in so far as it relates to my present invention, A indicates a controller-casing, in which are mounted the three controller drums or cylinders P, RS, and OS. These cylinders carry the rectangular contacts, which are shown in development in Fig. l and are arranged to be rotated, so that these contacts come into en-- gagement with a series of fixed fingers corresponding to the circular contacts shown in Fig. 1. These fingers are mounted in the customary manner, and for this reason it has been deemed unnecessary to illustrate them in the figures showing the construction of the controller. The reversing switch RS is thrown into one or the other of its operative positions by means of the handle RH. The power-switch P is rotated by means of a controller-handle, the lower portion of which is shown at PH. The comm utating-cylinder OS is mounted below the reversing-switch cylinder and is provided at its lower end with a cam-shaped plate D, having two adjacent notches n and 0 on the side toward the powercylinder. A spring 5 is fastened at one end to a pin 11 on the bracket E, which supports the lower bearing of the commutatingswitch, and at its other end is fastened to a pin 19 on the commutating-switch cylinder, these pinsbeing so positioned that as the conimutating-switch is moved from one to the other of its operative positions the spring will pass over the point about which the commutating-cylinder rotates, and will thus operate to throw it forcibly into either one of its operative positions and hold it there until the actuating means is again operated. Stops o and o are provided for limiting the throw of the switch. The shaft of the switch P carries at its lower end a cam 13, against which bears the head if of a memberF, which is suitably supported in a bearing in the upper end of a bracket m, projecting from the base of the controller. The member F carries at its outer end a pivoted pawl 1", which is normally held in the position shown in the drawings by means of the spring members s 8 A spring sis provided for maintaining the head tof the member F alwaysin engagement with the face of the cam B. The arrangement of the parts shown in Fig. 5 corresponds to the off position of the main cylinder P. If new this cylinder is rotated right-handedly, the surface of the cam B will operate to force the pawl '1' into engagement with the notch 0 in the plate D on the base of the commutating-switch and the commutating-switch will be rotated until the spring 3 passes over the center of support of the commutating-switch, after which the said switch will be thrown by the force of the spring into its other operative position. The switch will remain in this position throughout the movement of the controller, the member Rafter it has once been moved forward by the cam B, being held in its forward position throughout the movement of the controller until it is again returned to its ott position. The movement of the commutating-switch from the position shown in Fig. 5 into its other operative position will operate to bring the notch "a into such a position that when the member F is again projected forward the pawl '1 will engage the notch n and throw the commutatingswitch back into the position shown in the drawings. \Vhenever, therefore, the powercylinder P is returned to its off position and is again moved forward, the pawl T will engage one or the other of the notches n and 0, according to the position of the commutatingswitch, and will throw the said switch into its other operative position. In Fig. 4 I have also indicated in dotted lines how the commutating-switch may be operated from the reversing switch-cylinder instead of from the power-cylinder, and in Fig. 6 I have shown more in detail the mechanism which is illustrated in dotted lines in Fig. 4. Referring to this latter figure, G indicates a cam mounted on a shaftw,arranged to rotate with the reversing-switch. D is a notched plate similar in all respects to the plate D (shown in Fig. 5;) but in this case it is mounted on the upper end of the commutating-switch cylinder instead of below it. H is aslotted member having at one end a pin t, adapted to engage the edge of the cam G and at its other end a pin adapted to engage one or the other of the notches n and o. A spring 8 operates to maintain the pin t always in engagement with the cam G. This mechanism operates in the same manner as that shown in Fig. 5.

tively connected to one of the main controlling-switches of each controller is preferable when the grades are excessive or frequent or whenever they are heavier in one direction of running than in the other; but when the grades are substantially equal in both directions or whenever they are infrequent it may be sufficient if the arrangement of the motors in the tandem connection is reversed at each end of the run. In the latter case the separate commutating-switch in each controller may be dispensed with and the connections may be so arranged that the contacts of the powerswitch in one controller will perform the functions of one of the sets of contacts of the commutating-switch and the contacts of the power-switch in the other controller the f unctions of the other set. Such an arrangement is illustrated in Fig. 7 of the drawings, in which I have shown the two motors M and M connected by suitable wiring to the contacts of the two controllers G and 0 As shown in this figure, each controller comprises apower-switch Pand a reversing-switch RS, similar in construction to the corresponding switches shown in Fig. 1; but in place of the commutating-switch of Fig. 1 the wiring is so arranged that whenever the controller 0 is in operation the motor M will be motor No. 1 in the tandem connection and whenever the controller 0 is in operation the motor M will be No. 1 in the tandem connection. This result is accomplished by reversely connecting the windings a, b c and a b c of the motors to the two controllers. Supposing the reversing-switch RS of the controller 0' .to be thrown into such a position that its and 3 to the conductor 3 and thence through contacts 21 and 20 of the reversing-switch to the terminal of the winding a of the motor M. Starting from the conductor T a circuit may be traced through the contacts 2 and 4 to the conductor 4 and thence through contacts 19 and 18 of the reversing-switch to the terminal of the winding 1) of the motor M. The third circuit is through the common ground connection to which the source and the terminal of the winding 0 are connected. The windings d ef and d 6 f are connected by the controller-contacts the same as in the diagram of Fig. 1, and these connections need not therefore be described in connection with the present figure. The terminals of the windings a and I) of the motor M are connected through contacts 5 and 8 and 6 and 10 to the resistances R and R the terminal of the remaining winding 0 being connected through a common ground connection to the resistance R The connections above described are illustrated in Fig. 8 of the drawings, from which it will be seen that when ever the controller 0' is operated to connect the motors in tandem the motor M will be No. 1 in tandem connection. Supposingnow that the controller 0 is thrown to its off position and that the reversing switch of the controller (1 is thrown into such a position that its contacts 18 to 21 engage with the contacts marked a, if the powercylinder P of this controller is moved into its first operative position the motor-circuits will be so arranged that the motor M will be No. 1 in the tandem connection. For tracing the circuits it will be seen that a circuit leads from the conductor T through the contacts 1 and 3 of the power-switch to the conductor 3 and thence through contacts 19 and 18 of the reversing-switch to the terminal of the winding a of the motor M A circuit from the conductor T leads through contacts 2 and 4 of the power-switch to the conductor 4 and thence through contacts 21 and 20 of the reversing-switch to the terminal of the winding 11 of the motor M the connection between the source and the terminals of the winding 0 being made through the common ground connection. The windings cl, 6, and f and d e f of the two motors will be connected the same as when the other controller was in operation; but the other winding of the motor M will have its terminals connected through the controller-contacts and the ground connection to the resistances R R and R of the controller 0 The connections for the tandem position of this controller 0 are shown in Fig. 9 of the drawings, from which it will be seen that the motor M is No. 1 in the tandem connection.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In a control-circuit for a plurality of alternating-current induction-motors, means for connecting the motors in tandem with one or another of said motors as No. 1 in the tandem connection.

2. In a control-circuit for two alternatingcurrent induction-motors, means for connecting the motors in tandem with either one of said motors as No. 1 in the tandem connec tion.

3. In combination, a plurality of inductionmotors, circuit connections therefor, and controllers for the said motors having their contacts arranged to connect the motors in tandem with a different motor as No. 1 in the tandem connection when different contacts are in operative position.

4. In combination, a plurality of induction motors, and a control system therefor comprising one or more controllers provided with contacts arranged to connect said motors in tandem with one or another of said motors as No. 1 in the tandem connection.

5. In a control system for a plurality of induction-motors, controller-contacts arranged to connect said motors in tandem with one or another of said motors as No. 1 in the tandem connection.

6. In a control system for a plurality of induction-motors, controller-contacts arranged to connect said motors in tandem with either one of two of said motors as No. 1 in the tandem connection.

7. In a control system fora plurality of alternating-current induction-motors, a controller having its contacts arranged to connect said motors in tandem with one or another of said motors as No.1 in the tandem connection.

8. In combination, aplurality of inductionmotors, and a control system therefor comprising a plurality of controllers adapted to connect said motors in tandem, said controllers being constructed and arranged to periodically transpose the relative positions of the motors in the tandem connection.

9. In combination in a control system for induction-motors, a plurality of controllers each provided with cont-acts for connecting said motors in tandem, certain contacts of one controller being reversely connected with respect to the corresponding contacts of the other controller so that the different controllers will operate to connect the motors in tandem with a different motor as No. 1 in the tandem connection.

10. In combination in a control system for induction-motors, a plurality of controllers each provided with contacts for connecting a winding of one of said motors to a source of supply and for short-circuiting the corresponding winding of another motor on itself, the contacts of the two controllers being reversely connected to the said windings so that when one controller is operated to connect the motors in tandem, one motor will be No. 1 in the tandem connection and when the other controller is operated another motor will be No. 1.

11. In an induction-motor controller having its contacts arranged to connect a plu rality of motors in tandem, an auxiliary switch for changing the relation of the motors in the tandem connection.

12. In an induction-motor controller having contacts arranged to connect a plurality of motors in tandem, auxiliary contacts for changing the relation of the motors in the tandem connection.

13. In an induction-motor controller having its contacts arranged to connect a plurality of motors in tandem, an auxiliary switch provided with sets of contacts, one of which sets operates to connect one of the motors as No. 1 in .the tandem connection,

and another of which operates to connect another motor as No. 1.

14. In an induction-motor controller having its contacts arranged to connect a pinrality of motors in tandem, an auxiliary switch provided with contacts arranged to connect either one of two motors as motor No. l'in the tandem connection.

15. In an induction-motor controller having contacts for connecting a plurality of motors in tandem, an auxiliary switch for changing the relation of the motors in the tandem connection, and means whereby the movement of the main controller-handle operates the auxiliary switch.

16. In an induction-motor controller having contacts for connectinga plurality of mo tors in tandem, an auxiliary switch for changing the relation of the motors in the tandem connection, and means operatively related to one of the main controlling-switches for actuating said auxiliaryswitch.

17. In an induction-motor controller having contacts for connecting a plurality of motors in tandem, an auxiliary switch forchanging the relation of the motors in the tandem connection, means operatively related to one of the main controlling-switches for actuating said auxiliary switch, and means for maintaining said switch in the position into which it is thrown.

In witness whereof I have hereunto set my hand this etth day of April, 1901.

ALBERT H. ARMSTRONG. Witnesses:

BENJAMIN B. HULL, MARGARET E. WooLLnY. 

